Rubber-vulcanization accelerator



Patented Nov. 9, 1926.

UNITED STATES 1,606,321 PATENT ormce.

WINTFTELD SCOTT, 0E AxRon', omo, ASSIGNOR TO TiiE RUBBER SERVICE LAEoR-A- roEIEs 00., 0E AKRON, OHIO, A CORPORATION 0E OHIO.

RU EER-vuLCAnIzA'rIoN ACCELERATOR.

No Drawing.

The present invention is directed to an im the with the employment of a new type of compound for accomplishing this object.

' More specifically, the invention is directed to the use as rubber vulcanization accelerators of the various polysulfids of guanidine, and particularly of its di-aryl-substituted derivatives, according to the process hereinafter set forth, inwhich are described methods of manufacturing and using these new compounds. v

The polysulfids of guanidine and its derivatives ma be most readily manufactured by reacting ydrogen sulfid upon a mixture of sulfur and the guanidine, dissolved or suspended in any suitable solvent. Thus, for example, a mixture'of 210 parts of a guanidine derivative, such as di-phenyl guanidine, (or a corresponding amount of some other equivalent material) and 100 parts of sulfur,

are stirred into approximately 500 parts by weight of any desirable solvent, such as alcohol. The materials both dissolve to such an extent that, when hydrogen sulfid is led into the suspension, the alcoholic solution assumes a yellowish coloration, which is followed veryshortly by the precipitation of yellow crystals of the polysulfid. As the flow of hydrogen sulfid is continued, the undissolved sulfur and di-phenyl-guanidine pass into solution to react with the hydrogen sulfid until all the original mixture has been transformed into a polysulfid. It would, of course be possible, to use sufiicient solvent'to dissolve all the sulfur, and 'diphenyl-guanidine used, but this preferably is to be avoided, due to the possibility of a greater loss of solvent involved, and also to the loss of some of the product formed, because of its slight solubility in the solvent.

The loss of the product, due to solution in the s0lvent-= employed, may be reduced by using the same solvent, saturated with the product, and recovered fromone preparae tion, for the manufacture of successive batches of the material. An excess of hy.--

vis precipitated from the solution.

of the product thus obtained in a numberv of preparations, was found to average ap- Application filed December 17, 1924. Serial No. 758,625.

96% of the yield to be expected proximatel fieory as shown-icythe following from the t reaction:

wuim 2HN-C/ man.)

Although, in the above example, three atoms of sulfur are used for each molecule of di-phenyl-guanidine taken, it is, of course,

possible to use more or less sulfur, as desired. However, of the various polysulfids prepared, it was found that the compound obtained by reacting hydrogen sulfid upon a mixture of one molecule of di-phenylwhen hydrogen sulfid is led into an alcoholic suspension of the proper guanidine derivative and sulfur in the manner as described. Similarly, the polysulfids of all the alkyl and aryl substituted gu'anidines may be prepared. It is apparent that various polysulfids of the same substituted guanidine may be obtained by varying-the proporti-on'of sulfur'to guanidine taken.

Other methods of preparing my preferred type of compound, may, of course, be employed. For example, it is possible to prepare a solution of a guanidine, such as diphenylsguanidine, saturate this solution with hydrogen sulfid, and then dissolve the necessary quantity of sulfur in the solution, whereupon the Y guanidine polysulfid is formed. Or it is possible to add a solution of sodium, potassium, or ammonium or other soluble polysulfid to di-phenyl guanidine or other guanidine dissolved in. a suitable solvent, and the polysulfid derivative thereof and are allprecipitated as very fine crystals v to advantage as vulcanization accelerators in a number of different types of rubber compounds. the following example is given as illustrative of one means of utilizing these materials. One hundred parts of rubber, for example, the grade known to the trade as smoked sheets, 5 parts of zinc oxide, 8.5 parts of sulfur. and 0.5 parts of accelerator are compounded together in the usual manner on the rubber mixing mills, and the mix is then vulcanized, preferably under 40 pounds steam pressure per square inch, in the well known manner,

Although any of the guanidine poly-sulfiCls may be used in the example as shown, the advantages and characteristics of this class of accelerators are most readily illustrated by means of the following table,

wherein A, B, C respectively represent rubber compositions'of the type illustrated, and employ as accelerators the di-phenyl-guanidine polysulfids prepared by using 1, 2, and 3 atoms of sulfur, respectively, for each molecule of di-phenyl-guanidine taken, and then reacting the mixture with hydrogen sulfid in the manner already described.

Timfilof cure Modulus 3t- Teln- Per at 40 s. steam s1 9 pressure per Stock. 300%. at 58111:; sq. in. 500%. 700%. break.

15 minutes. A 100 198 547 1570 952 B j 118 185 419 1480 970 C 105 188 410 1588 1010 30 minutes A 139 396 1210 2530 880 B 170 376 1020 2400 875 C 160 320 868 2310 907 45 A 205 478 1596 2820 835 B 192 452 1405 2760 865 C 171 403 1190 2720 870 1 hour A 210 616 2260 3190 800 B 214 58 2050 3195 840 C 221 54 1595 2995 830 It is evident from the above table, that ing properties. In the above tests, the most favorable results are realized after curing the mixture fora period varying from approximately 45 minutes to one hour under a steam pressure of 40 pounds per square inch. Polysulfids of other substituted guanidines, particularly those derived from di-o-tolylguanidine, di-m-xylyl-guanidine, as well as of other aryl-substituted' guanidines, show equally valuable and desirable accelerating qualities. All of these .guanidine polysulfids will withstand higher working temperatures without decomposition, are denser, and give less trouble from dusting than does diphenyl-guanidine,, when used as an accelorator of vulcanization. I

I do not wholly limit my claims to the specific method of preparation of the guanidine polysulfids given, nor to definite amounts of the accelerator used in the rubber mix, or with the various compounding ingredients which maybe used in therubber mix. Nor do I limit my invention solely to the compounds mentioned, or by any theory advanced by way of explanation, or in any way except by the claims attached hereto.

\Vhen my preferred accelerators are prepared by some methods, it is possible that the polysulfids obtained may contain a suflicient quantity of free sulfur so that an additional quantity of this agent is not needed When-the product is used for the manufacture of a vulcanized rubber. In other words, by imposing certain conditions in the preparation of the polysulfid, it is possible to obtain an accelerator containing enough available sulfur so that the reaction product when mixed by itself with rubber and zinc oxide and the mixture is heated under pressure, a vulcanized rubber product results.

What I claim is 1. The process of vulcanizing .rubber which comprises heating rubber and sulfur in the presence of a compuond resulting from the union of two parts of di-phenylguanidine four parts of sulfur, and one part of hydrogen sulfid.

2. The process of vulcanizing rubberwhich comprises plasticizing rubber, mixing therewith sulphur and a small amount of diphenyl-guanidine polysulfid and vulcanizing the mixture. I

3. The process of vulcanizing rubber which comprises plasticizing rubber, mixing therewith sulphur and a small amount of d'i-aryl-substituted guanidine polysulfid and .vulcanizing the mixture.

4. The process of vulcanizing rubber therewith sulphur and a small amount of the polysulfid of substituted guanidines and vulcanizing the mixture.

5. The process of vulcanizmg rubber which comprises plasticizing rubber, mixing therewith sulphur and a small amount ofguanidine polysulfid and vulcanizing the mixture.

6. The process of vulcanizing rubber which comprises plasticizing rubber, mixing therewith sulphur and a small amount of a compound obtained by tpassing hydrogen sulfid into a solution of dl-phenyl-guanidine and sulfur and vulcanizing the mixture.

7. The process of vulcanizing rubber which comprises plasticizing rubber, mixing therewith sulphur and a small amount of a compound formed by passing hydrogen sulfid into a solution of a substituted guanidine and sulfur and vulcanizing the mixture.

8. A rubber product comprising the vulcanization product 'of a mixture of rubber with av vulcanizing agent and a .compound resulting from the union of two parts of the product obtained by mixing a mixture of rubber with a vulcanizing'agent and diphenyl guanidine polysulfid and vulcanizing the mixture. I

10. A composition of matter comprising the product obtained by mixing a mixture of rubber with a vulcamzing agent and a diaryl-substituted guanidine polysulfid and vulcanizing the mixture.

11. A composition of matter comprising the product obtained by mixing a mixture of rubber with a vulcanizing agent and the polysulfid of a substituted guanidine and vulcanizing the mixture.

12. A composition of matter comprising the product obtained by mixing a mixture of rubber with a vulcanizing a nt and guanidine polysuliid and vulcanlzing the mixture.

13. A composition of matter comprising the product obtained by mixing a mixture of rubber with a vulcanizing agent and a compound obtained b passing hydrogen sulfid into a solution 0 di-phenyl-guanidine and sulfur and vulcanizing the mixture.

14. A composition of matter comprising the product obtained by mixing a mixture of rubber with avulcanizing agent and a com- .pound obtained by passing hydrogen sulfid into a solution of a substituted guanidine and sulfur and vulcanizing the mixture.

15. The process of vulcanizing rubber which comprises plasticizing rubber, mixing therewith guanidine polysulfid, and vulcanizing the mixture.

16. The process of vulcanizing rubber which comprises plasticizing rubber, mixing therewith sulphur and a small amount of a hydrogen sulfid derivative of guanidine, and vulcanizing the mixture.

171 The process of vulcanizing rubber which comprises plasticizing rubber,vmixing therewith sulphur and a. small amount of hydrogen sulfid derivative of di-phenylguanidine, and vulcanizing the mixture.

In testimony whereof I. afiix my signature.

fwmrmnn soon. 

